The present disclosure relates to a method and apparatus for detection of a disconnection of the power grid. More particularly, the present disclosure relates to islanding and the prevention thereof.
Islanding of a grid-connected distributed generator (DG) occurs when a section of the grid containing the DG is disconnected from the main utility, but the DG continues to energize the grid lines in the isolated section (termed as an island). For example, consider a DG system connected to a feeder through a transformer. A load (not owned by the DG owner) is also connected to the same feeder through another transformer. If a grid disconnect device (circuit breaker, recloser, fuse, or sectionalizer) opens, it is possible for the DG to continue to supply current to the isolated section of the grid. This is islanding, and the isolated section of the grid being powered by the DG system is referred to as an island.
Accordingly, there is a continuing desire for a method and controller that prevent islanding.